Vibration-actuated micro mirror device
A vibration-actuated micro mirror device comprises a substrate, a swinging frame, a reflection mirror, and a vibration part. The swinging frame is rotatably arranged within a first accommodating space formed on the substrate. The reflection mirror is rotatably arranged within a second accommodating space formed on the swinging frame. The vibration part further comprises a plate coupled to the substrate, and a first and a second vibration structures. The first and the second vibration structures are coupled to the plate and are spaced a distance away from each other, wherein the first vibration structure receives a first driving signal having a first frequency and the second vibration structure receives a second driving signal having a second frequency smaller than the first frequency, thereby enabling the swinging frame to rotate about the first axis while enabling the reflection mirror to rotate about the second axis.
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The present application is a continuation-in-part of U.S. patent application Ser. No. 13/450,574, filed on Apr. 19, 2012, now U.S. Pat. No. 8,325,405, which is a divisional application of U.S. patent application Ser. No. 12/963,024, filed on Dec. 8, 2010, now U.S. Pat. No. 8,218,214, which claims priority from Taiwan Patent Application No. 099127428 filed in the Taiwan Patent Office on Aug. 17, 2010, the entire disclosures of which are incorporated herein by reference.
TECHNICAL FIELDThe present disclosure relates to a micro mirror technology, and more particularly, to a vibration-actuated micro mirror device.
BACKGROUNDWith rapidly increasing demand for micro projectors, there are more and more manufacturers that are directing their resources and funding toward the related researches in order to establishing a leading position in this promising and profitable technology. It is noted that micro projectors can be integrated into all kinds of electronic devices, such as cellular phones and notebook computers. By a modularization design of micro projector, any cellular phone can be equipped with a projector module and thus can be used in briefing easily and conveniently that is comparatively much more capable of attracting consumer interest than those without. Most micro projectors that are currently available on the market are flat in appearance, and consequently, all the components used in micro projectors are designed solely for reducing the thickness of the micro projectors, by that not only the flat and thin micro projectors can be portable, but also can be easily integrated with other products.
One of the key issues for producing a good micro projector is to have a refection mirror that can be driven to rotate within a large angular range and at high rotation frequency. For a XGA projector displaying a resolution of 800 pixels by 600 pixels to achieve 30 frames per second, its fast axis must be capable operating at 18 kHz or higher, and the faster the better. Conventionally, there are three different methods for actuating reflection mirrors in micro projectors, which are an electromagnetic-actuated method, an electrostatic-actuated method and a piezoelectric-actuated method, and accordingly, the reflection mirror should be configured differently in corresponding to the way it is being actuated.
In U.S. Pat. No. 7,442,918, a micro-electro-mechanical system (MEMS) device is disclosed, which utilizes a MEMS process for electroplating double layer planar coils simultaneously on its mirror and out ring relating respectively to the fast scan axis and the slow scan axis so as to enable the fast and the slow scan axes to be actuated by the Lorentz force induced from the interaction between the coils and the permanent magnets disposed at two opposite sides thereof as soon as the coils are charged. Moreover, in U.S. Pat. No. 7,659,918, a single-axis scanning device is disclosed, in which a reflection mirror that is disposed in the middle of the device is actuated to pivotally oscillate or rotate by the use of a piezoelectric material, or by the vibration induced surrounding the reflection mirror. In addition, there is another single-axis scanning device disclosed in U.S. Pat. No. 7,446,919, in that there are four piezoelectric elements being used for actuating a reflection mirror to rotate as the reflection mirror is disposed in the middle of the device.
SUMMARYThe present disclosure related to a high-frequency vibration-actuated micro mirror device with ultra-thin and low-power design, which utilizes a high frequency driving signal and a low frequency driving signal to actuate two vibration structures in respective. Thereby, the two vibration structures, being actuated by the two driving signals, are enabled to generate respectively two vibration wave signals that are to be transmitted to a substrate configured with a fast-axis swinging frame and a slow-axis reflection mirror for enabling the swinging frame and the reflection mirror to resonant and thus to rotate accordingly. Since the pivotally oscillating of the slow-axis reflection mirror can be induced by low-frequency wave signals while the pivotally oscillating of the fast-axis swinging frame can be induced by high-frequency wave signals, a two-dimensional scanning operation can be achieved by the swinging frame and reflection mirror that are being actuated to rotate and thus a specific projection effect can be achieved.
In an exemplary embodiment, the present disclosure provides a vibration-actuated micro mirror device, comprising a substrate, a swinging frame, a reflection mirror, and a vibration part. The substrate having a first accommodating space. The swinging frame is disposed within the first accommodating space and is rotatably coupled to a first peripheral side wall defined the first accommodating space through a first shaft about a first axis, the swinging frame further comprising a second accommodating space. The reflection mirror is disposed within the second accommodating space and is rotatably coupled to a second peripheral side wall defined the second accommodating space through a second shaft about a second axis perpendicular to the first axis. The vibration part further comprises a plate, and a first and a second vibration structures. The plate has a first surface coupled to the substrate, and a second surface opposite to the first surface. The first and a second vibration structures are respectively coupled to the second surface and are spaced a distance away from each other, wherein at least a part of the first and second vibration structures are corresponding to the substrate. The first vibration structure receives a first driving signal having a first frequency and the second vibration structure receives a second driving signal having a second frequency smaller than the first frequency, thereby enabling the swinging frame to rotate about the first axis through twist of the first shaft while enabling the reflection mirror to rotate about the second axis through twist of the second shaft.
Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description.
The present disclosure will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present disclosure and wherein:
For your esteemed members of reviewing committee to further understand and recognize the fulfilled functions and structural characteristics of the disclosure, several exemplary embodiments cooperating with detailed description are presented as the follows.
Please refer to
The swinging frame 21 is disposed within the first accommodating space 200, and is rotatably coupled to the first peripheral side wall defined the first accommodating space 200 through a first shaft 210 about the first axis X. In the present embodiment, the first shaft 210 further has a first subshaft 2100, and a second subshaft 2101 respectively protruding out from two opposite sides of the swinging frame 21 to connect to the two opposite second side walls 202 of the first accommodating space 200. In addition, the swinging frame 21 further has a second accommodating space 211 formed therein for receiving the reflection mirror 22. The second accommodating space 211 is defined by a second peripheral side wall. Likewise, in the present embodiment, the second peripheral side wall is formed as a rectangular shape, which is formed by two opposite third side walls 212 parallel to the first axis X and two opposite fourth side walls 213 parallel to the second axis Y, wherein two ends of each fourth side wall 213 are respective connected to the two opposite third side walls 212. It is noted that the shape formed by the second peripheral side wall should not be limited to the rectangular shape, and it can be changed according to the need.
The reflection mirror 22 is disposed within the second accommodating space 211 and is rotatably coupled to the second peripheral side wall defined the second accommodating space 211 through a second shaft 220 about the second axis Y perpendicular to the first axis X. In the present embodiment, the second shaft 220 further has a third subshaft 2200, and a fourth subshaft 2201 respectively protruding out from two opposite sides of the reflection mirror 22 to connect to the two opposite third sides 212 of the second accommodating space 211.
In addition to the arrangement of the first shaft 210 and the second shaft 220 shown in
Back to the
Referring back to
Referring back to
In addition to the structure of unimorph, alternative embodiment having bimorph structure is also provided in
Please refer to
The following description relates to how the vibration structures are to be driven to vibrate by taking the vibration-actuated micro mirror device illustrated in
Please refer to
In addition, please refer to
In
The following description relates to how the swinging frame and reflection mirror are to be driven to rotate in the present disclosure that is illustrated by defining the first driving signal is a high frequency signal while the second driving signal is a low-frequency signal, and thus the driving signals are similarly to those shown in
wherein If represents a mass moment of inertia of the reflection mirror 22 with respect to the second axis Y, and kf represents a torsional stiffness of the second shaft 220 about the second axis Y. It is noted that when the frequency of the first driving signal 90 is close to or substantially the same as the natural resonant frequency of the second shaft 220, a larger rotation angle can be achieved. Accordingly, the twist of the second shaft 220 about the second axis Y is enabled by the contribution of the first driving signal 90.
As shown in
wherein Is represents a mass moment of inertia with respect to the combination of swinging frame 21 and the reflection mirror 22 about the first axis X, and ks, represents a torsional stiffness of the first shaft 210 about the first axis X. It is noted that when the frequency of the second driving signal 91 is close to or substantially the same as the natural resonant frequency of the first shaft 210, a larger rotation angle can be achieved. Accordingly, the twist of the first shaft 210 about the first axis X is enabled by the contribution of the second driving signal 91.
By the vibrations of the first and the second vibration structures 231, 232, the twists of the first shaft 210 and the second shaft 220 can be controlled and consequently, the angles of the swinging frame 21 and the reflection mirror 22 are adjusted accordingly so as to achieve a specific scanning operation. It is noted that although the first shaft 210 and second shaft 220 in both the embodiments of
With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the disclosure, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present disclosure.
Claims
1. A vibration-actuated micro mirror device, comprising:
- a substrate having a first accommodating space;
- a swinging frame, disposed within the first accommodating space and rotatably coupled to a first peripheral side wall defined the first accommodating space through a first shaft about a first axis, the swinging frame further comprising a second accommodating space;
- a reflection mirror, disposed within the second accommodating space and rotatably coupled to a second peripheral side wall defined the second accommodating space through a second shaft about a second axis perpendicular to the first axis; and
- a vibration part further comprising: a plate having a first surface coupled to the substrate, and a second surface opposite to the first surface; and a first and a second vibration structures respectively coupled to the second surface and spaced a distance away from each other, wherein at least a part of the first and second vibration structures are corresponding to the substrate;
- wherein the first vibration structure receives a first driving signal having a first frequency and the second vibration structure receives a second driving signal having a second frequency smaller than the first frequency, thereby enabling the swinging frame to rotate about the first axis through twist of the first shaft while enabling the reflection mirror to rotate about the second axis through twist of the second shaft.
2. The vibration-actuated micro mirror device of claim 1, wherein a first slot is formed on the substrate for dividing the substrate into a first area coupled to the first vibration structure, and a second area coupled to the second vibration structure.
3. The vibration-actuated micro mirror device of claim 1, wherein the plate is a metal plate.
4. The vibration-actuated micro mirror device of claim 3, wherein the first and the second vibration structures are made of a piezoelectric material whereby the first vibration structure and the plate are combined to be formed as a first unimorph, and the second vibration structure and the plate are combined to be formed as a second unimorph.
5. The vibration-actuated micro mirror device of claim 1, wherein the plate is a non-metal plate having an electrically conductive film coated on the second surface.
6. The vibration-actuated micro mirror device of claim 5, wherein the first and the second vibration structures are made of a piezoelectric material whereby the first vibration structure and the plate are combined to be formed as a first unimorph, and the second vibration structure and the plate are combined to be formed as a second unimorph.
7. The vibration-actuated micro mirror device of claim 1, wherein the plate further comprising a second slot having openings communicating with each other and the openings respectively being formed at the first surface, the second surface, and a lateral side wall in a thickness direction of the plate, wherein the first vibration structure and the second vibration structure are respectively arranged at two sides of the second slot on the second surface.
8. The vibration-actuated micro mirror device of claim 7, wherein a length of the second slot along the first axis is equal to another length of the first and second vibration structures along the first axis.
9. The vibration-actuated micro mirror device of claim 7, wherein a chamfer structure is formed on a connection area between inner walls formed the second slot.
10. The vibration-actuated micro mirror device of claim 1, wherein the second shaft is configured in a manner selected from a group consisting of: a center axis of the second shaft is aligned passing through the center of the reflection mirror, and another center axis of the second shaft is aligned another distance away from the center of the reflection mirror.
11. The vibration-actuated micro mirror device of claim 1, wherein the plate is configured to be a common grounding electrode of the first and the second vibration structures.
12. The vibration-actuated micro mirror device of claim 1, wherein the first surface of the plate corresponding to the first vibration structure further comprises a third vibration structure coupled to the substrate while the first surface of the plate corresponding to the second vibration structure further comprises a fourth vibration structure coupled to the substrate.
13. The vibration-actuated micro mirror device of claim 12, wherein the plate is a metal plate.
14. The vibration-actuated micro mirror device of claim 13, wherein the first, second, third and fourth vibration structures are respectively made of a piezoelectric material whereby the first vibration structure, the third vibration structure and the plate are combined to be formed as a first bimorph, and the second vibration structure, the fourth vibration structure and the plate are combined to be formed as a second bimorph.
15. The vibration-actuated micro mirror device of claim 12, wherein the plate is a non-metal plate having an electrically conductive film coated on the second surface.
16. The vibration-actuated micro mirror device of claim 15, wherein the first, second, third and fourth vibration structures are made of a piezoelectric material whereby the first vibration structure, the third vibration structure and the plate are combined to be formed as a first bimorph, and the second vibration structure, the fourth vibration structure and the plate are combined to be formed as a second bimorph.
17. The vibration-actuated micro mirror device of claim 12, wherein the first driving signal is delivered to the first and third vibration structures while the second driving signal is delivered to the second and fourth vibration structures.
18. The vibration-actuated micro mirror device of claim 1, wherein the first frequency of the first driving signal is more than or equal to 15 KHz.
19. The vibration-actuated micro mirror device of claim 1, wherein the second frequency of the second driving signal is less than or equal to 1.5 KHz.
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Type: Grant
Filed: Nov 2, 2012
Date of Patent: Aug 13, 2013
Patent Publication Number: 20130057936
Assignee: Industrial Technology Research Institute (Hsin-Chu)
Inventors: Yu-Jen Wang (Taipei County), Chien-Shien Yeh (Tainan County), Chung-De Chen (Miaoli County), Hung-Chung Li (Hualien County)
Primary Examiner: James Phan
Application Number: 13/667,093
International Classification: G02B 26/08 (20060101);